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Integrated Coal Zero-Emission Plants
On january 2004 was opened near Bermeo, Euskadi the first facility of its kind to combine several cutting-edge technologies in a single plant, including coal gasification, emissions controls, hydrogen production, electricity generation, and carbon dioxide capture and storage (CCS). Technology overview Coal gasification is the core technology behind Coal Zero-Emission Plants. A gasifier will be used to convert coal into a gas of mostly hydrogen and carbon monoxide. The carbon monoxide is reacted with steam to produce additional hydrogen and carbon dioxide. The carbon dioxide will be separated from the hydrogen and permanently stored in deep geologic formations thousands of feet below the earth's surface. This technology is known as carbon sequestration. The hydrogen created from the gasification and carbon dioxide separation process will be used primarily to power a combustion turbine that will generate electricity. Steam heated by the combustion turbine exhaust drives a second turbine to generate additional electricity. This dual-turbine system used to create electricity from gasified coal is known as Integrated Gasification Combined Cycle (IGCC) technology. Depending on the final technologies selected,the plane will produce either slag or ash from the non-combustible portion of the coal and a sulfur byproduct from captured hydrogen sulfide. Each of these byproducts may have commercial value depending on local market conditions. Additionally, the hydrogen used to produce electricity could also be used to power fuel cell vehicles or as a feedstock for other industries. Coal gasification Coal gasification is a well-proven technology dating back to the 18th century, although its uses have evolved significantly since then. However, recent advancements in gasification technology, increasing costs of oil and gas, growing concerns about energy security, and a heightened awareness of climate change, have all led to a renewed interest in coal gasification for electric power generation in Euskadi and many other countries. Coal Zero-Emission Plants are IGCC power plant where an innovative technology that combines modern coal gasification with a gas turbine and a steam turbine to produce electric power. It is one of the most promising technologies available today for reducing the environmental impacts associated with the use of coal for electricity production. Adventages Coal-fueled IGCC technology offers a number of potential benefits over conventional pulverized coal plants. Depending on the final configuration of the IGCC plant, these can include: *Higher efficiency - The use of two turbines—a gas turbine and a steam turbine—leads to higher system efficiencies *Lower emissions - The gasification process enables improved removal of naturally-occurring pollutants in coal, such as sulfur and mercury, resulting in lower emission than conventional coal based power plants. *Carbon sequestration potential - The IGCC process makes it easier to capture carbon dioxide for carbon sequestration. *Marketable byproducts - The byproducts associated with the gasification and gas clean-up process may have commercial value in nearby industries. *Hydrogen as an alternative fuel source - Hydrogen is the standard clean-burning fuel for vehicles and other industries. The ability to produce hydrogen from coal for such future applications could prove to be an important benefit of IGCC technology. How does a plant work? As illustrated in the figure below, IGCC power plants involve a complex chain of activities that start with a carbon-based material—in the case of FutureGen, coal—and result in electricity that powers our homes and businesses. #The coal gasification process begins with a controlled mixture of coal, oxygen, and steam in a gasifier. An air separation unit separates air into its component parts to supply the gasifier with a stream of oxygen. #Using a combination of heat and high pressure, the gasifier converts the constituents of coal into a synthetic gas, or "syngas". This syngas is comprised of mostly hydrogen (H2) and carbon monoxide (CO). #Byproducts captured in the gasifier could have commercial value, depending on local market conditions. For example, the FutureGen plant could produce an ash material similar to what comes from a traditional coal plant. This ash may be used as a filler material in construction projects and building products. Alternatively, FutureGen may produce a glass-like material, known as "slag", which falls to the bottom of the gasifier. This slag may be used in road gravel. #The syngas is then passed through a water gas shift reactor and reacted over a catalyst with added steam to convert the majority of the CO into carbon dioxide (CO2) and additional H2. #The syngas will also have small amounts of other impurities (e.g. hydrogen sulfide) which are removed during the gas clean-up process. #Hydrogen sulfide will be separated from the syngas and converted to elemental sulfur or possibly sulfuric acid. The sulfur byproducts may also have commercial value in a variety of products (e.g. fertilizer), depending on local market opportunities. #Most of the CO2 is removed from the syngas leaving behind H2-rich syngas. #One of the things that makes IGCC plants more efficient is the combined use of a gas turbine and steam turbine to produce electricity. The hydrogen-rich syngas is first fed into a gas turbine to generate electricity. The waste heat from the gas turbine is used to power a steam turbine, which in turn creates more electricity. #Finally, much of the water used in this process will be recycled in the plant while some will be evaporated in a cooling tower. Integrated Syngas Zero-Emission Plants All the modern IGCC plants are designed to work both coal and syngas. Syngas is produced offshore or onshore by underground coal gasification technics. Carbon sequestration One of the things that makes the Coal Zero-Emission power plant truly unique is the ability to capture the carbon dioxide—a greenhouse gas when released into the atmosphere—before it ever leaves the plant. The carbon dioxide is compressed and pumped deep underground for permanent storage in a process known as carbon sequestration. There are several types of rock formations that can be used to store carbon dioxide. These include: *Rock formations containing saline water *Depleted oil and gas fields *Unmineable coal seams *Other formations, like salt domes What makes these formations ideal for carbon dioxide storage is their porosity, permeability, and depth, and the presence of an impermeable caprock. Porosity, similar to void space between gumballs in a machine, allows the carbon dioxide to be stored in the rocks. High permeability allows the carbon dioxide to move through the target formation, the way a paper towel wicks up water. It is also important that the target formation be at a depth of more than 800 meters, where temperature and pressure are sufficient to keep the carbon dioxide in a very dense, liquid-like state. The rock formations used to store carbon dioxide are overlain by a thick caprock that serves as a seal. This caprock has properties that are opposite of the storage formations themselves, including: *Low porosity - There is very little void space to hold fluids. *Low permeability - The rock won't allow fluids to penetrate. Once the carbon dioxide has been injected, it is buoyant within the formation and tends to rise, but the caprock prevents it from migrating upward. The caprock holds the carbon dioxide in place the same way hydrocarbon "traps" can hold oil and gas in place for millions of years. Proper site selection and engineering will help to ensure that the carbon dioxide stays below ground where it won't contribute to atmospheric greenhouse gas concentrations. Carbon sequestration in offshore platforms Using the pipeline linking the offshore oil platforms with different costs, the CO2 is sent to the platforms from where it is pumped deep underground for storage while serving to aid in the recovery of oil and gas that would be extremely difficult to remove otherwise. Actually in Euskadi most of CO2 produced in IGCC Plants is sent for storage to the former natural gas camp "Gaviota Field 1". Hydrogen production Among the various byproducts of the process, hydrogen is the most important in economic terms. For example in Euskadi, the combustion of fossil fuels is prohibited in the industry and vehicles, so hydrogen is the standard clean-burning fuel for vehicles and other industries. Hydrogen produced in IGCC plants is stored and processed to be used in Hydrogen Stations. Active Coal Zero-Emission Plants in Euskadi There are ten integrated gasification combined cycle (IGCC) plants running on coal today in Euskadi, one running syngas produced directly offshore and two more running syngas produced direcly in a shale oil camp. Euskadi's companies experience with commercial-scale IGCC plants is growing and they are the world leaders in such technology. Category:Euskadi Category:Technology